The present invention relates to an improvement in electronic equipment with a solar cell.
Electronic equipment with a solar cell generally has a secondary cell which is charged by an electromotive force of the solar cell therein. An electronic circuit and other load circuits are operated by using the electromotive force charged in the secondary cell.
A certain type of electronic equipment can only be used in the presence of light. For example, a compact electronic calculator using a liquid crystal display device of a light receiving type is known. In such electronic equipment, the secondary cell is not generally used. A capacitor with a small capacitance for smoothing an output voltage of the solar cell is only connected in parallel with the solar cell. The electromotive force of the solar cell is directly supplied to the electronic equipment.
However, a secondary cell such as a silver oxide cell is generally expensive and requires a large mounting space. For this reason, electronic equipment using a secondary cell is expensive and bulky. In addition, when the secondary cell can no longer be recharged the replacement thereof is cumbersome. Furthermore, an electronic circuit may be damaged by liquid leakage from the secondary cell.
Needless to say, the electronic equipment with a solar cell cannot be used in a dark place since no power is generated. For this reason, a system such as an electronic wristwatch which must be continuously operated regardless of the presence/absence of light cannot comprise an electronic circuit of this configuration. For example, a device such as a compact electronic calculator which is used in a bright place may have a storage unit for storing data such as names, telephone numbers, addresses and the like. In such a device, when no voltage is supplied to the storage unit, data stored therein is erased. Thus, such electronic equipment requires a secondary cell.